What is back billing and why does it matter now?
Back billing is when your energy supplier charges you for gas or electricity you used months ago but never actually billed you for at the time. It usually lands as a shock, a letter or an app notification demanding hundreds of pounds for usage going back over a year. Often it is a meter reading mix up or a supplier system error, not anything you did wrong. With so many households reviewing their direct debits around the autumn price cap change, it is worth knowing exactly where you stand before an old charge turns up.
There is a limit, though. Ofgem, the energy regulator, sets a firm cap on back billing, restricting how far a supplier can reach into your history, and it applies to every domestic gas and electricity account.
The 12 month back billing rule explained
Ofgem’s back billing rule says that if your supplier is at fault for not billing you correctly, it cannot charge you for energy used more than 12 months ago. This covers situations where a supplier failed to send bills at all despite you asking, relied on estimated readings instead of ones you or a meter reader actually submitted, or muddled up readings between properties.
The rule exists to stop the Do Nothing Default working in the supplier’s favour. Let an account drift for two or three years, then try to claw it all back in one go? That’s on them, not you. The 12 month cutoff has applied to all domestic and microbusiness suppliers since Ofgem’s ruling came into force, and it still stands in 2026.
- Applies to gas and electricity accounts on standard domestic contracts.
- Covers unbilled usage, not unpaid bills you already received and ignored.
- The supplier carries the cost of its own billing failure beyond 12 months.
When can your supplier still back bill you?
Your supplier can still charge you for older usage if you are the reason accurate billing was not possible in the first place. That mainly covers blocking access to your meter, tampering with it, or repeatedly ignoring requests to provide a reading when no smart meter is fitted.
In those cases, the 12 month back billing protection does not apply, and a supplier can in theory go back much further to recover the debt. It is a narrow exception rather than the norm. Suppliers still need to show they made reasonable efforts to bill you along the way.
One more thing worth flagging. If you received an accurate bill and simply did not pay it, that is a debt issue, not a back billing dispute, and the 12 month rule will not help you argue it away.
What to do if you get a back bill
Start with the date. If any part of the charge covers energy used more than 12 months before the bill date, and the delay was down to the supplier, you can challenge that portion under the back billing rule. Ask the supplier directly whether the charge falls within the protected period, and ask for a written breakdown of the usage and dates involved.
Then gather your own evidence. Old meter readings, screenshots from your online account, or dated photos of your meter all help show what you were actually using and when. If you have taken regular readings, a meter reading history is often the quickest way to settle a dispute.
If the supplier will not budge and you believe the charge breaches the rule, you can escalate a formal complaint. If it is not resolved within eight weeks, or you reach deadlock, you can take it to the Energy Ombudsman, who can order the supplier to write off charges that fall outside the protected period.
How do I avoid a back billing surprise in the first place?
Mostly, you avoid a back billing shock by not letting a supplier lose track of your account. Submit a meter reading whenever you can, even if you are not asked to. Check that the figure on your bill roughly matches what you can see on the meter itself.
A smart meter removes most of the guesswork, since readings are sent automatically rather than estimated. If you are still on a traditional meter, switching to a smart meter is one of the simplest ways to stop estimated billing building up into a nasty surprise later.
It also helps to actually read your bill instead of filing it away unopened. Compare the estimated usage figure against your own readings each quarter and you will catch a billing error within weeks, not years. Our guide to understanding your energy bill walks through what each section actually means.
Key takeaways
- Suppliers cannot back bill you for energy used more than 12 months ago if the delay was their fault.
- The rule does not cover bills you already received and simply did not pay.
- Blocking meter access is one of the few situations where the 12 month limit will not apply.
- Regular meter readings are your best evidence if a back bill ever lands.
- Unresolved complaints can go to the Energy Ombudsman after eight weeks.
- Can my energy supplier back bill me for two years of usage?
- Only for the most recent 12 months if the delay was the supplier’s fault. Anything older than that should be written off under Ofgem’s back billing rule, unless you blocked access to the meter.
- Does the back billing rule apply to gas and electricity?
- Yes, it applies to both fuels on domestic accounts, and to microbusinesses too, regardless of which supplier you are with.
- What if I never gave a meter reading?
- Not providing readings is not the same as blocking access. Suppliers are still expected to estimate reasonably and chase you for accurate figures, so the 12 month protection can still apply.
- Will switching supplier affect an existing back bill dispute?
- No. A back bill dispute sits with the supplier who issued it, and switching does not cancel a genuine debt, though it does stop the same estimating problem happening again.
- How do I complain about a back billing charge?
- Raise it with your supplier in writing first, quoting the 12 month back billing rule. If it is not resolved within eight weeks, escalate to the Energy Ombudsman for a free, independent decision.
